1. Field of the Invention
The present invention relates generally to a mobile communication system, and in particular, to a paging apparatus and method in a mobile communication system providing an MBMS (Multimedia Broadcast Multicast Service).
2. Description of the Related Art
CDMA (Code Division Multiple Access) generally uses a plurality of physical channels. The physical channels are common channels and dedicated channels. The common channels are shared among a plurality of UEs (User Equipments) within a cell area of a Node B, and the dedicated channels are assigned to particular UEs by the Node B. The common channels include a CPICH (Common Pilot Channel), a P-CCPCH (Primary Common Control Physical Channel), an S-CCPCH (Secondary Common Control Physical Channel), and a PICH (Paging Indicator Channel). The dedicated channels include a DPCH (Dedicated Physical channel).
In CDMA, broadcasting channels broadcast information to UEs. There are different broadcasting channels in a CDMA mobile communication system, for example, in a Release 99 mobile communication system. They are a BCH (Broadcasting Channel) and an FACH (Forward Access Channel). The BCH broadcasts SI (System Information) required for cell access to UEs, and the FACH sends control information about assignment of a dedicated channel and a broadcast message to a particular UE in addition to the function of the BCH. Since the main use of the broadcasting channels is to deliver common control information to UEs and control information to a particular UE, transmission of user data on the broadcasting channels is limited.
Recently, the development of communication technology has brought with it multicast multimedia communication that enables transmission of a large amount of data, such as packet data and circuit data, in addition to voice service in CDMA mobile communication systems. Thus many multicast multimedia applications have been proposed. Particularly, the MBMS has emerged as a future generation mobile communication service. The MBMS is a service that provides audio data and video data contemporaneously. Since the MBMS requires a large amount of transmission resources and is likely to cause concurrent provision of different services within a Node B on a large scale, it is provided on broadcasting channels. BMC (Broadcast Multicast Control), a single channel sharing technique, is free of constraints of temporal delay since it is applied to low rate transmission such as text broadcasting. As compared to the BMC, the MBMS is provided at a very high data rate and is sensitive to temporal delay. Therefore, the MBMS must be serviced in a different way from the BMC.
When transmitting a signal on a radio channel, the signal is modulated with a carrier having a higher frequency than the signal itself prior to transmission in order to improve transmission characteristics against external noise in a typical mobile communication system. Hence, the conventional CDMA mobile communication system sends physical channels available to a Node B with one carrier. In other words, both common channels and dedicated channels are transmitted with one carrier. However, resources are not sufficient to provide existing services in the conventional CDMA mobile communication system. Accordingly, it is obvious that the provision of the MBMS will lead to a further lack of resources.
In this context, studies have been conducted on a solution to the lack of resources to support the future generation mobile communication system requiring a large amount of resources.